Pre-eclampsia is estimated to affect about 5% of deliveries while eclampsia affects about 1.4% of deliveries.[5] In the developed world rates are about 1 in 2,000 deliveries due to improved medical care.[1] Hypertensive disorders of pregnancy are one of the most common causes of death in pregnancy.[10] They resulted in 46,900 deaths in 2015.[6] Around one percent of women with eclampsia die.[1] The word "eclampsia" is from the Greek term for lightning.[11] The first known description of the condition was by Hippocrates in the 5th century BCE.[11]

Either in the epigastric region (the center of the abdomen above the navel, or belly-button)

And/or in the right upper quadrant of the abdomen (below the right side of the rib cage)

Altered mental status (confusion)

Any of these symptoms may present before or after a seizure occurs.[14] It is also possible that none of these symptoms will develop.

Other cerebral signs may immediately precede the convulsion, such as nausea, vomiting, headaches, and cortical blindness. If the complication of multi-organ failure ensues, signs and symptoms of those failing organs will appear, such as abdominal pain, jaundice, shortness of breath, and diminished urine output.

The seizures of eclampsia typically present during pregnancy and prior to delivery (the antepartum period), but may also occur during labor and delivery (the intrapartum period) or after the baby has been delivered (the postpartum period).[12][14][15] If postpartum seizures develop, it is most likely to occur within the first 48 hours after delivery. However, late postpartum seizures of eclampsia may occur as late as 4 weeks after delivery.[12][14]

There are risks to both the mother and the unborn child (fetus) when eclampsia occurs. The fetus may grow more slowly than normal within the womb (uterus) of a woman with eclampsia, which is termed intrauterine growth restriction and may result in the child appearing small for gestational age or being born with low birth weight.[16] Eclampsia may cause problems with the placenta to occur. The placenta may bleed (hemorrhage) or it may begin to separate from the wall of the uterus.[17] It is normal for the placenta to separate from the uterine wall during delivery, but it is abnormal for it to separate prior to delivery; this condition is called placental abruption and can be dangerous for the fetus.[18]Placental insufficiency may also occur, a state in which the placenta fails to support appropriate fetal development because it cannot deliver the necessary amount of oxygen or nutrients to the fetus.[17] During an eclamptic seizure, the beating of the fetal heart may become slower than normal (bradycardia).[16][19] If any of these complications occurs, fetal distress may develop. If the risk to the health of the fetus or the mother is high, the definitive treatment for eclampsia is delivery of the baby. It may be safer to deliver the infant preterm than to wait for the full 40 weeks of fetal development to finish, and as a result prematurity is also a potential complication of eclampsia.[17][20]

In the mother, changes in vision may occur as a result of eclampsia, and these changes may include blurry vision, one-sided blindness (either temporary due to amaurosis fugax or potentially permanent due to retinal detachment), or cortical blindness, which affects the vision from both eyes.[21][22] There are also potential complications in the lungs. The woman may have fluid slowly collecting in the lungs in a process known as pulmonary edema.[17] During an eclamptic seizure, it is possible for a person to vomit the contents of the stomach and to inhale some of this material in a process known as aspiration.[16] If aspiration occurs, the woman may experience difficulty breathing immediately or could develop an infection in the lungs later, called aspiration pneumonia.[14][23] It is also possible that during a seizure breathing will stop temporarily or become inefficient, and the amount of oxygen reaching the woman's body and brain will be decreased (in a state known as hypoxia).[14][24] If it becomes difficult for the woman to breathe, she may need to have her breathing temporarily supported by an assistive device in a process called mechanical ventilation. In some severe eclampsia cases, the mother may become weak and sluggish (lethargy) or even comatose.[22] These may be signs that the brain is swelling (cerebral edema) or bleeding (intracerebral hemorrhage).[17][22]

Eclampsia, like pre-eclampsia, tends to occur more commonly in first pregnancies.[25][26][27] Women who have long term high blood pressure before becoming pregnant have a greater risk of pre-eclampsia.[25][26] Furthermore, women with other pre-existing vascular diseases (diabetes or nephropathy) or thrombophilic diseases such as the antiphospholipid syndrome are at higher risk to develop pre-eclampsia and eclampsia.[25][26] Having a large placenta (multiple gestation, hydatidiform mole) also predisposes women to eclampsia.[25][26][28] In addition, there is a genetic component: a woman whose mother or sister had the condition is at higher risk than otherwise.[29] Women who have experienced eclampsia are at increased risk for pre-eclampsia/eclampsia in a later pregnancy.[26]

Diagram of the placenta and its position in the uterus during pregnancy

Image of a placenta after delivery

The presence of a placenta is required, and eclampsia resolves if it is removed.[30] Reduced blood flow to the placenta (placental hypoperfusion) is a key feature of the process. It is accompanied by increased sensitivity of the maternal vasculature to agents which cause constriction of the small arteries, leading to reduced blood flow to multiple organs. Also, an activation of the coagulation cascade may lead to microthrombi formation, which can further impair blood flow. Thirdly, increased vascular permeability results in the shift of extracellular fluid from the blood to the interstitial space, with further reduction in blood flow, and edema. These events lead to hypertension; renal, pulmonary, and hepatic dysfunction; and cerebral edema with cerebral dysfunction and convulsions.[30] Before symptoms appear, increased platelet and endothelial activation[30] may be detected.

Placental hypoperfusion is linked to abnormal modelling of the fetal–maternal placental interface that may be immunologically mediated.[30] The invasion of the trophoblast appears to be incomplete.[31]
The placenta produces the potent vasodilator adrenomedullin: it is reduced in pre-eclampsia and eclampsia.[32] Other vasodilators are also reduced, including prostacyclin, thromboxane A2, nitric oxide, and endothelins, also leading to vasoconstriction.[19]

The hallmark symptom of eclampsia is a seizure,[15] and the steps for diagnosing eclampsia depend on what is already known at the time when the seizure occurs.

If a pregnant woman has already been diagnosed with pre-eclampsia during the current pregnancy and then develops a seizure, she may be assigned a 'clinical diagnosis' of eclampsia without further workup. This means that a diagnosis of eclampsia is most likely given the symptoms and medical history, and eclampsia can be assumed to be the correct diagnosis until proven otherwise.[35] However, if a woman has a seizure and it is unknown whether or not she has pre-eclampsia, testing can help make the diagnosis clear.

One of the core features of pre-eclampsia is high blood pressure. Blood pressure is a measurement of two numbers. If either the top number (systolic blood pressure) is greater than 140 mmHg or the bottom number (diastolic blood pressure) is greater than 90 mmHg, then the blood pressure is higher than the normal range and the person has high blood pressure. If the systolic blood pressure is greater than 160 or the diastolic pressure is greater than 110, the hypertension is considered to be severe.[12]

Another core feature of pre-eclampsia is proteinuria, which is the presence of excess protein in the urine. To determine if proteinuria is present, the urine can be collected and tested for protein; if there is 0.3 grams of protein or more in the urine of a pregnant woman collected over 24 hours, this is one of the diagnostic criteria for pre-eclampsia and raises the suspicion that a seizure is due to eclampsia.[12]

In cases of severe eclampsia or pre-eclampsia, the level of platelets in the blood can be low in a condition termed thrombocytopenia.[36][19] A complete blood count, or CBC, is a test of the blood that can be performed to check platelet levels.

Convulsions during pregnancy that are unrelated to pre-eclampsia need to be distinguished from eclampsia. Such disorders include seizure disorders as well as brain tumor, aneurysm of the brain, and medication- or drug-related seizures. Usually the presence of the signs of severe pre-eclampsia precede and accompany eclampsia, facilitating the diagnosis.

Detection and management of pre-eclampsia is critical to reduce the risk of eclampsia. The USPSTF recommends regular checking of blood pressure through pregnancy in order to detect preeclampsia.[37] Appropriate management of women with pre-eclampsia generally involves the use of magnesium sulfate to prevent convulsions.

The four goals of the treatment of eclampsia are to stop and prevent further convulsions, to control the elevated blood pressure, to deliver the baby as promptly as possible, and to monitor closely for the onset of multi-organ failure.

Convulsions are prevented and treated using magnesium sulfate.[38] The study demonstrating the effectiveness of magnesium sulfate for the management of eclampsia was first published in 1955.[39] Serum magnesium concentrations associated with maternal toxicity as well as neonatal respiratory depression, low muscle tone, and low Apgar scores[40] are:

With intravenous administration the onset of anticonvulsant action is fast and lasts about 30 minutes. Following intramuscular administration the onset of action is about one hour and lasts for three to four hours. Effective anticonvulsant serum levels range from 2.5 to 7.5 mEq/liter. Magnesium is excreted solely by the kidneys at a rate proportional to the plasma concentration and glomerular filtration.[41]

Even with therapeutic serum magnesium concentrations, recurrent convulsions may occur, and additional magnesium may be needed, but with close monitoring for respiratory, cardiac, and neurological depression. If magnesium administration with resultant high serum concentrations fail to control convulsions, the addition of other intravenous anticonvulsants may be used, facilitate intubation and mechanical ventilation, and to avoid magnesium toxicity including maternal thoracic muscle paralysis.

The agents of choice for blood pressure control during eclampsia are hydralazine and/or labetalol.[19] This is because of their effectiveness, lack of negative effects on the fetus, and mechanism of action.

If the baby has not yet been delivered, steps need to be taken to stabilize the woman and deliver her speedily. This needs to be done even if the baby is immature, as the eclamptic condition is unsafe for both baby and mother. As eclampsia is a manifestation of a type of non-infectious multiorgan dysfunction or failure, other organs (liver, kidney, lungs, cardiovascular system, and coagulation system) need to be assessed in preparation for a delivery (often a caesarean section), unless the woman is already in advanced labor. Regional anesthesia for caesarean section is contraindicated when a coagulopathy has developed.

In Downton Abbey, an historical drama television series, the character Lady Sybil dies (in season 3, episode 5) of eclampsia shortly after child birth.[47]

In Call the Midwife, a medical drama television series set in London in the 1950s and 1960s, the character (in season 1, episode 4) named Margaret Jones is struck with pre-eclampsia, ultimately proceeding from a comatose condition to death. The term "toxemia" was also used for the condition, in the dialogue.[48]

In House M.D., a medical drama television series set in the U.S., Dr. Cuddy, the hospital director, adopts a baby whose teenage mother dies from eclampsia and had no other parental figures available.[48]